A Survey of Sorghum Covered Kernel Smut Disease Infection in Western Kenya

Covered kernel smut is a seed borne panicle disease caused by the fungus Sporisoriumsorghi which is classified within the Ustilaginales, class Basidiomycetes. An extensive survey was conducted across six counties (Busia, Siaya, Vihiga, Kisumu, Homa-Bay and Migori) in western Kenya during the long rain season of March- August 2018 when sorghum was at physiological maturity in order to: (i) determine occurrence and distribution of the covered kernel smut disease (CKSD) in western Kenya (ii) identify possible sources of resistance to the CKSD in farmers fields and (iii) determine the cropping systems under which sorghum is grown in the region. A total of 100 farmers sorghum fields were surveyed in the six counties. Average incidence ( %) of the disease was obtained from a sample of 20 plants selected in a 4by 4msquare plot area using simple random sampling technique from each farm visited. Sorghum was grown either as sole or as intercrop with common beans, groundnut, cowpeas and mung beans, with cowpeas intercrops dominating across the farms. Disease incidence was relatively higher on the shorter and early maturing varieties (Nyadundo 1 and 2, C26 and MUK27) compared to the taller ones (T53B, MUK154, N68, T30B, IS3092) suggesting a potential relationship between sorghum variety and the disease incidence based on the height or maturity period of the sorghum. Further discussions with farmers and observations made indicated that the CKSD was present only during anthesis and grain filling stage and virtually absent at the seedling stage. The higher disease incidence on the shorter varieties resulted into more than 90 % of the sorghum panicle being infested hence the urgent need to put in place control measures to curb spread of the disease. Farmers were advised to use improved cultural practices such as burning to destroying the infected crop residues, Chemical method of seed dressing using relevant fungicides and using clean planting materials as quick remedies. However, long term alternatives include breeding for tolerance to the CKSD which our sorghum breeding program has started to pursue. It is expected that some of the sources of resistance identified in this study will be used to introgression disease resistance into the farmer preferred susceptible varieties.